Problem: If $x \oslash y = 3x-y$ and $x \boxdot y = 2x-8y$, find $-2 \oslash (-5 \boxdot 4)$.
First, find $-5 \boxdot 4$ $ -5 \boxdot 4 = (2)(-5)-(8)(4)$ $ \hphantom{-5 \boxdot 4} = -42$ Now, find $-2 \oslash -42$ $ -2 \oslash -42 = (3)(-2)-(-42)$ $ \hphantom{-2 \oslash -42} = 36$.